Aluminum alloys are typically utilized for wheel and brake components on an aircraft. For example, aluminum alloys that are commonly used in wheel structures for aircraft include Aluminum Association Series alloys 2014-T6, 2040-T6 and 7050-T74. These alloys are specific alloys within the Aluminum Association Series of alloy classes 2XXX and 7XXX, respectively. These alloys are attractive due to their high strength and fracture toughness characteristics. Although the 2XXX and 7XXX aluminum alloys exhibit high strength characteristics, they are more prone to corrosion than other aluminum alloys. This corrosion includes general corrosion, pitting, stress corrosion cracking, and intergranular attack.
To counteract the problems related to corrosion, aluminum aircraft wheel and brake components are provided with a hard anodized coating. One type of accepted hard-anodized coating involves the application of a sulfuric acid anodic coating in combination with a sodium dichromate sealant to the aluminum surface. Thereafter, depending on the type of wheel assembly and the manufacturer's recommendations, portions of the wheel or brake may be further coated over the hard anodizing with the application of a primer. Other portions of the wheel may be further coated with a paint type topcoat.
One common type of aircraft wheel includes an inner wheel half and an outer wheel half. Bolts, washers and nuts hold the two halves together while an o-ring seals the joint between the two wheel halves. The inner wheel half additionally includes drive lugs or inserts for the interaction with the brake assemblies, and may include heat shields to reduce the transfer of brake heat to the wheel. An inner bore extends through both halves of the wheel and is constructed and arranged to house at least two bearing and seal assemblies, and may further be constructed to include retaining rings, grease retainers or the like. In addition, either half of the wheel may include sensors, thermal relief plugs, over-inflation plugs or the like that require ports or bores that extend through the thickness of the wheel. Another type of aircraft wheel includes an inner wheel half and an outer wheel half. The inner and outer halves are held together by a split ring.
Current maintenance practices for aircraft wheels require inspections of aircraft wheels at predetermined intervals and for various reasons. For example, inspections may be required for wheels that have exceeded a predetermined number of landings or have had a predetermined number of tire changes; or the aircraft may have suffered a catastrophic tire failure or an inspection may be required at annual aircraft inspections. While some of these inspections are simply visual inspections that can be accomplished by merely removing the tire from the rim, others require surface coatings to be removed for non-destructive testing (NDT). For example, a fluorescent penetrant inspection (FPI) is required during every major overhaul. In order to perform this inspection, the paint must be removed from the wheel. Following NDT inspection, provided the wheel checks to standards, the primers, lubricants and topcoats are reapplied to the wheel. The task of stripping and reapplying the paint for FPI inspection during maintenance and overhaul is labor intensive and significantly increases the cost of maintaining the aircraft.
In general, paint is removed from the wheel using chemical paint remover, or media blast equipment utilizing media like walnut shells, plastic, water or other media suitable for removing lubricant, primer and topcoat without damaging the hard anodized coating of the wheel or brake. The technician then refers to a manual for requirements relating to primer and/or topcoat coatings for the component. Different manufacturers and wheel constructions have different requirement as to which portions of the wheel get the various coatings. In a typical scenario, a technician will apply masking tape, paper, cardboard etc. to portions of a hard-anodized component such as a wheel that is devoid of other surface coatings. Any unwanted tape is thereafter trimmed away with a razor knife until the desired area is masked from receiving primer. The wheel will then be coated with a primer, via an air type spray gun, and dried. This step may be further complicated with the requirement of applying primer to both sides of the wheel which may require an extra drying cycle. After completion of the primer step, additional portions of the wheel will be masked with tape and trimmed with razor blades for application of a topcoat. The tape and any glue that remains attached to the wheel must be removed with solvents without damaging the primer or topcoat. The wheel can thereafter be assembled and shipped to a desired location for installation on an aircraft until the next inspection is required.
Therefore, there is a need in the art for a system of masking components that are adapted for temporary attachment to various aluminum components, such as aircraft wheels or brake components. The masking components should allow portions of the component to be masked from receiving unwanted surface coatings during an air gun spraying operation. The masking components should also be designed to be added over other masking components sequentially to allow for multiple coatings which may not be over the same portions of the component without removal of the masking components used for earlier coatings. The components should be easily removed after coating the component for reuse on other like constructed components. The masking components should also be constructed from a material that allows easy removal of prior coatings to allow for extended use of the masking components.